Method of manufacturing an improved simulated leather and the leather product manufactured therefrom

ABSTRACT

Method of manufacturing an improved simulated leather and the product leather are described. In the method, a low-foam polyolefin sheet is quenched immediately after its emergence from an extrusion die and the quenched side of said sheet is subjected to corona discharge. An adhesive agent is applied to the treated side and, after drying, a thermoplastic synthetic resin film or sheet is laminated to said surface.

I United States Patent [151 3,661,671 Katagiri et al. [4 May 9, 1972 54]METHOD OF MANUFACTURING AN [56] References Cited IMPROVED SIMULATEDLEATHER UNITED STATES PATENTS AND THE LEATHER PRODUCT 3 255 061 6/1966 Dbb 156/79 o s MANUFACTURED THEREFROM 3,262,805 7/ 1966 Aoki 156/79 [72]Inventors: Keizo Katagiri; Kenji Kuroishi; Kazuchika 3,123,508 1964Waugh Nakamura; Katsutoshi Hagiwara, all of 3,391,044 7/1968 Kaghan eta1. 156/272 Katsuta, Japan 3,239,399 3/1966 King 156/272 [73] Asslgnee:Nippon Kakoh Seishi K.K., Tokyo, Japan Primary Emminer Carl D. Quarfonh[22] Filed: Feb. 20, 1970 Assistant E.\'aminerS. R. Hellman [2]] pp No:13,207 Attorney1(e1man and Berman [57] ABSTRACT [30] Foreign ApphcanonPnomy Dam Method of manufacturing an improved simulated leather and Feb.21, 1969 Japan ..44/12513 the product lea h r r describedn h m a mpolyolefin sheet is quenched immediately after its emergence [52] U.S.C1 ..156/78, 156/272, 156/244 from an extrusion die and the quenchedside of said sheet is [5 1 Int. Cl ..B32b 5/18 subjected to coronadischarge. [58] Field of Search 156/78 An adhesive agent is applied tothe treated side and, after dry.

ing, a thermoplastic synthetic resin film or sheet is laminated to saidsurface.

7 Claims, No Drawings METHOD OF MANUFACTURING AN IMPROVED SIMULATEDLEATHER AND THE LEATHER PRODUCT MANUFACTURED THEREFROM BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to a methodof manufacturing a simulated leather comprised of a polyolefin foamhaving a thermoplastic resin film or sheet laminated thereon, and to thesimulated leather that is obtainable by said method.

2. Description of the Prior Art It is well known that polyolefin foamsare manufactured by impregnating polyolefins, such as polypropylene,polyethylene, etc., with a foaming agent, solvent and other additivesand that those foams are used in the manufacture of bags and cases,sandal tops and other formed articles. However, because of thedisadvantage that it is not conducive to the color tones required ofsuch end products as bags, cases and footwear, it has been commonpractice to laminate the foam to other resin films or sheets. Thetrouble is that the nonpolarity of polyolefins prevents them fromaffording adequate bonding strength.

The conventional foamed polyolefin sheets, particularly those of foamedpolyethylene, are too porous to be colored attractive shades, besidesbeing vulnerable to scratches and abrasion. To overcome thoseshortcomings, there has been suggested a method wherein the surface offoamed polyethylene is covered with a composition based on athermoplastic resin such as polyvinyl chloride resin through theintermediary of an adhesive agent in order to impart adequate scratchand wear resistance to the foam, as well as for the purpose of improvingthe color appeal of the product. It has so far been found, however, thatonly an inadequate bond can be obtained between foamed polyolefin and athermoplastic resin sheet to yield a practically unsuitable product.

SUMMARY OF THE INVENTION It is an object of the invention to provide amethod for overcoming the foregoing disadvantages.

Another object is to provide simulated leather which is scratch andabrasion-resistant and has an attractive color tone.

The invention, therefore, relates to a method for producing an improvedsimulated leather consisting in a foamed polyolefin having a surfacecovering of a thermoplastic resin film or sheet, such as of polyvinylchloride, vinyl chloridevinyl acetate copolymer, ethylene-vinylacetate-vinyl chloride terpolymer, polyurethane, polyamide or polyaminoacid resin, said foamed polyolefin having a foaming rate of 1.5 to 3times, or an apparent density in the range from 0.3 to 0.6 g/cm. In asecond aspect, the invention relates to the simulated leather soproduced.

DETAILED DESCRIPTION OF THE INVENTION In the method of the instantinvention, a polyolefin sheet surface which has been treated under theparticular set of conditions to be described hereinafter is joined witha thermoplastic resin film or sheet through the intermediary of anadhesive agent to produce a firmly bonded laminate. Polyolefin resinsgenerally are non-polar polymers and accordingly afford only a pooraffinity for other resins. As a result, to impart polarity to the formerpolymers, the surfaces of such resins are conventionally treated bycorona discharge. It is also an established art to use polyurethaneresin as said adhesive agent. Actually, however, even if a foamedpolyolefin sheet is treated by corona discharge and, then, laminated toa polyvinyl chloride-based composition with the aid of such an adhesive,no adequate bonding strength can be expected.

The term polyolefin as used herein means any and all of polyethylene,polypropylene, and ethylene-propylene copolymer, but for the convenienceof explanation, the invention will hereinafter be particularly describedby reference to polyethylene, it being understood, however, that theinvention is by no means limited to the art and product involvingpolyethylene alone.

Polyethylene beads are impregnated with a low-boiling solvent atatmospheric or slightly elevated pressure, followed by the addition ofan organic foaming agent and inorganic one and, if necessary, of apigment. The formulation is inflationextruded into a foamed polyethylenesheet at a temperature above a softening point thereof. In thisoperation, immediately after the hot sheet emerges from the dieassembly, one side of the sheet is brought into contact with awater-cooling tube surface. This quench may be accomplished as well byimmersing the sheet in cooling water, in which case both sides of thesheet are quenched. In the latter case, no adverse effect is found,either, on the quality of the sheet. The above novel finding has givenimpetus to the development of the instant invention.

. The quenching of a sheet is carried out under the following If afoamed polyethylene sheet is allowed to cool in the air gradually afterits emergence from the extruder, the resulting cell structure of thesheet is different from that of a similar film which has been quenched.This finding is supported by microscopic examination of a cross sectionof the sheet.

- Thus, whereas the cell structure of the quenched side is similar tothat of the inner sheet portion, the gradually cooled sheet does notshow cells on the cooled surface.

In the latter sheet, the cells exist only under a skin. A bondingstrength test was conducted to evaluate the relative merits of the twocell structures. Each test piece was treated by corona discharge and,then, coated with a thermosetting polyurethane resin g'oatingcomposition. After drying, a flexible polyvinyl chloride film or sheetwas laminated onto the coated surface of the test piece over rollers.The bonding strength of the laminate was measured by means of a tensiontester at 200 mm/min. It was found that whereas the gradually cooledsample showed a strength value of 1.5- 3.0 kg/3 cm, the quenched sampleof the invention had a value greater than 8.0 9.0 kg/3 cm (The foamedpolyethylene layer failed at the above value).

Corona discharge is carried out under the following condit1ons:

distance between the electrodes 2-3 mm high-frequency voltage 1.5-5 KVhigh-frequency current 0.5-1 .2 A sheet moving speed 3-6 m/min However,it was also found that some quenched samples prepared by buffing thesurface of the polyethylene foam to expose the cells and subjecting thesurface to a corona discharge gave a low bond strength value of 2 to 3kg/ 3 cm.

It is therefore not that the surface cells are the exclusive factor inthe improved bond strength, but the crystallinity of the materialpolyethylene also appears to be responsible for the improvement. Asynergistic effect of this crystallinity with corona-discharge treatmentis a probable cause.

The invention will be further described in detail with reference to apreferred example thereof.

A low-foam polyethylene having a foaming rate from 1.5 to 3 times wasemployed. That is, it had an apparent density of 0.3 to 0.6 g/cm". Thispolyethylene was extruded at a temperature substantially higher than itssoftening point and quenched, and the quenched side of the sheet wassubjected to a corona discharge. Separately, an isocyanate-modifiedpolyester coating composition (solid 20 percent) is admixed with atn'functional isocyanate compound, followed by the addition of ethylacetate. The mixture is stirred well, and after viscosity adjustmentwith ethyl acetate, the adhesive is applied to the sheet with a doctorknife at the rate of 30 to 40 g/m. Then, a plasticizer, stabilizer,pigment and other conventional additives are incorporated into polyvinylchloride resin to prepare a flexible polyvinyl chloride compound in ablender,

EXAMPLE l Polyethylene of the following formulation was extruded underthe conditions given below.

Formulation:

polyethylene (density 0.92, M.I. (melt index) 1.2)

(containing petroleum ether) azoisobutyrodinitrile 100 parts citric acid0.10 parts sodium bicarbonate 0.30 parts pigments 3.0 parts One side ofthe resulting sheet of foamed polyethylene was quenched from the dietemperature of 160 C., while moving at 4 m/min by contact with a,cooling tube having a temperature of C. for sec. and subjected to coronadischarge from between electrodes spaced 2 mm at 2 KV and 0.8 A whilemoving at 4 m/min. High-Frequency Electrical Appliances3 KW Type (asmanufactured and marketed by Kasuga Electric Co., Ltd.) was used as thepower source. The following adhesive composition was coated onto thetreated surface with a doctor knife.

Hydroxy terminated mixed polyester prepolymer modified with diisocyanate(Trade name BOSTlC 4154, as produced and marketed by Bostic Japan, Ltd.)parts l-lexanetriol-tritolylene diisocyanate (Trade name BOSCODUR R, asproduced and marketed by Bostic Japan, Ltd.) 2 parts Ethylacetate 56parts Toluene 8 pans The coating rate of the adhesive composition was 30g/m, and the coated sheet was dried in a furnace at 100 120 cC.Thereafter, the following flexible compound was sheeted out into athickness of about 0.15 mm and laminated onto the adhesive surface ofsaid coatedsheet.

Polyvinyl chloride resin (Trade name P (polymerization degree) 1050, asproduced and marketed by Mitsui- Tohatsu, Ltd.)

Dioctyl phthalate 40 parts Stabilizers Cd-stearate 2 parts Ba--stearate1 part Epoxy-soybean oil 2 parts Pigments 3 parts The bonding strengthof the laminate, as measured by the method described above, was greaterthan 8.0 kg/3 cm. It was also found that the foam was spoiled.

EXAMPLE 2 A polypropylene composition of the following formulation wasextruded under the conditions given below.

Formulation:

100 parts polypropylene (density 0.94, M.I. 0.3) containing liquidpropane) 100 parts Azodicarbonamide 0.1 part Cadmium stearate 0.5 partsOne side of the resulting foamed sheet was quenched from a dietemperature of 230 C., while moving at 5 m/min by contact with a coolingtube at 5 C. during 12 sec, and subjected to corona discharge fromelectrodes spaced 2 mm at 2.5 KV and 0.6 A. The same adhesivecomposition, drying and coating as in Example 1 were applied, and thecoated sheet was laminated onto the following composition into athickness of 0.15 mm on a calender.

Composition:

v inyl chloride-vinyl acetate (9 5/5) copolymer, I

100 parts Dioctyl phthalate 15 parts Dibutyl phthalate 15 partsCd-stearate 2 parts Ba-stearate 1 part Epoxy-soybean oil 3 pans Pigments3 parts The resulting product was embossed. The bonding strength wasgreater than 8.0 kg/3 cm. It was also found that the foam was spoiled.

EXAMPLE 3 One side of the same foamed polyethylene sheet as in Example 1was quenched by passage through a water-cooling bath from a dietemperature of 240 C. at 5 m/min. The cooling water temperature was 10C., and the cooling time 12 sec. One side of the quenched sheet wassubjected to corona discharge as in Example 1. The same adhesivecomposition, drying and coating as in Example 1 were applied, and thefollowing composition was the same process by in Example 1.

Composition:

Ethylene-acetate-vinyl chloride graft terpolymer 100 parts Dioctylphthalate 10 parts Stearic acid 0.3 parts Cd-stearate 2 partsBa-stearate 1 part Pigments 3 parts The resulting product was embossed.The bonding strength was greater than 8.0 kg/3 cm. It was also foundthat the foam was spoiled.

EXAMPLE 4 The following solution was spread on the adhesive coated sheetsurface of polyethylene foam as in Example 1 with a doctor knife at therate of 150 g/m.

Acryloid A-101 (acrylic resin, Rohm & Haasmade) 40 parts Vinylchloride-vinyl acetate (/15) copolymer (P 300) 20 parts Celluloseacetate-butylate 5 pans Dioctyl phthalate 20 parts Pigments 17 partsMethyl ethyl-ketone 180 parts Ethyl acetate 80 parts The coated sheetwas dried at C., and finally embossed at C. The resulting product wassatisfactory as the product obtained according to the method in Example1.

EXAMPLE 5 N-methoxy-Nylon (Methoxy content 7.0%) 40 parts Santicizer-8(Toluene sulphonic acid derivative) 4 parts Toluene 36 parts Methanol 1l2 pans Water 16 parts Citric acid 1.2 parts Pigments 8 parts Thecomposition was cast onto a sheet of release paper coated with melamineresin to a thickness of about 0.1 mm to about 150 g/m, and dried at 110C. A sample of the same polyethylene sheet foam as in Example 1 wasquenched and treated by corona discharge in the same manner as inExample 3 and was coated with the same adhesive composition as inExample 1, whereupon it was heated to about 120 C. Thereafter the samplewas laminated onto the nylon sheet, while said sheet of release paperwas peeled off. The product was embossed at 120 C. The bonding strengthwas very good.

EXAMPLE 6 The following materials were dissolved in ethylacetate and thesolution was adjusted to 5,000 c.p. to 7,000 c.p.

Desmolin N (HO-terminated mixed polyester prepolymer modified with Thesolution was treated in a manner similar to the method followed inExample 5. The bonding strength was excellent.

EXAMPLE 7 The following composition was treated in a manner similar tothe method followed in Example 5 Poly 'y -methylglutamate (Polyaminoacidresin, 10% solution in trichlor-ethane, Trade name Aji-Coat-ZOO, asproduced and marketed by Ajinomoto Co., Ltd.)

Pigments 100 parts 10 parts The bonding strength was very good.

CONTROL EXAMPLE As a control, foamed polyethylene was allowed to cool atroom temperature (25 C.). Otherwise, it was treated in the same manneras Example 1.

The bonding strength of the resulting laminate, as measured in themanner hereinbefore described, was 2.2 2.9 kg/3 cm, or an average of 2.5kg/3 cm.

On the other hand, when the corona discharge treatment was omitted fromthe procedure of Example 1, the foam could not be bonded to flexiblepolyvinyl chloride.

What is claimed is:

l. A method of manufacturing a laminate which comprises:

a. extruding a sheet of polyolefin foam having an apparent density of0.3 to 0.6 g/cm from a die at a temperature substantially higher thanthe softening point of said 'polyolefin;

b. quenching a face of the extruded sheet from said temperature at arate sufficient substantially to maintain the cell structure of theextruded foam in the quenched face;

c. subjecting said face to corona discharge until receptive to athermosetting, synthetic-resin, adhesive composition;

d. thereafter coating said face with said composition; and

e. laminating a film of thermoplastic synthetic resin to the coated faceat a temperature sufiicient to set said composition.

2. A method according to claim 1, wherein said polyolefin is selectedfrom the group consisting of polyethylene, polypropylene, andethylene-propylene copolymer.

3. A method according to claim 1, wherein said thermoplastic syntheticresin is selected from the group consisting of v polyvinyl chlorideresin, vinyl chloride-vinyl acetate copolymer, ethylene-vinylacetate-vinyl chloride terpolymer, polyurethane resin, polyamide resinand polyamino acid resin.

4. A method as set forth in claim 1, wherein said face is quenched bycontact with a heat conductive solid surface having a temperature of 4to 15 C. during at least 10 seconds.

5. A method as set forth in claim 4, wherein said face is quenched bycontact with said surface while said sheet travels over said surface ata rate of 3 6 meter per minute.

6. A method as set forth in claim 5, wherein said contact is maintainedfor 10 to 15 seconds.

7. A method as set forth in claim 1, wherein said polyolefin ispolyethylene and said sheet is extruded at C.

2. A method according to claim 1, wherein said polyolefin is selectedfrom the group consisting of polyethylene, polypropylene, andethylene-propylene copolymer.
 3. A method according to claim 1, whereinsaid thermoplastic synthetic resin is selected from the group consistingof polyvinyl chloride resin, vinyl chloride-vinyl acetate copolymer,ethylene-vinyl acetate-vinyl chloride terpolymer, polyurethane resin,polyamide resin and polyamino acid resin.
 4. A method as set forth inclaim 1, wherein said face is quenched by contact with a heat conductivesolid surface having a temperature of 4* to 15* C. during at least 10seconds.
 5. A method as set forth in claim 4, wherein said face isquenched by contact with said surface while said sheet travels over saidsurface at a rate of 3 6 meter per minute.
 6. A method as set forth inclaim 5, wherein said contact is maintained for 10 to 15 seconds.
 7. Amethod as set forth in claim 1, wherein said polyolefin is polyethyleneand said sheet is extruded at 160* C.